An ion channel is essential means for sustaining life in all living cells. An ion channel continues to transport ions through cell membranes. Main functions of ion channels are essential for sensory organs to maintain homeostasis.
Basically, when a receptor is stimulated and activated from various environmental forces such as heat, light, smell, sound, and pressure, an ion channel provides an electrical signal generated by ion motion across a cell membrane to a nerve.
Until now, several research groups have reported performances of nature-inspired artificial ion channel sensors. Among the performances, there is almost no pressure sensing using an ion channel system. In the biological field, it is known that mechanotransduction corresponds to mechanical stimuli in mechanosensory receptors that change in cell membrane potential. In mechanosensory receptors, a stimulus may be deflection of a hair-cell stereocilia in a cochlea.
In particular, although the exact mechanism is not yet known, a stretch-activated ion channel is one of the pressure-detectable configurations which exist in microbes, yeast, and plants.
Most studies for pressure sensing are limited to silicon and polymer-based devices. These devices may include a transistor, pressure sensing, capacitive sensing, piezoelectric sensing, piezoresistive, and optical sensing.
These systems are coupled to input/output regions which cause unstable electrical properties, low selectivity, high operating power, and static feeling. For example, the main concern of piezoelectric sensors results from a high internal resistance and is affected by an input impedance of a readout electrical circuit and low sensitivity to temperature and static force.
Capacitive sensors suffer from disadvantages that noise is associated with an electric field interaction and fringe effect causing the demand of a particular electronic circuit should be removed.
A biological ion channel system configured to sense external stimuli basically includes receptors and nanopores. The hybrid design of ion channels is effectively evolving. The receptor is mechanically triggered by an external stimulus, and the nanopore electrochemically performs a function to provide a path for ion transport. The two elements are separated from each other. Ion channels have important properties, as follows. First, the ion channel is passive in the sense that it does not need an energy source to operate them. Second, highly selective recognition of substrates with high receptivity is provided. Moreover, a direct signal is obtained from ion transport across a membrane along an electrochemical gradient without an additional amplifier system or electronic circuit. An ion channel is configured to carry ions at a very high speed (more than 106 s−1 for ions and less than 109 s−1 for water) in a nanoscale or microscale dimension without concern about energy consumption. Thus, an ion channel may be used as a sensors to monitor physical parameters including acceleration, temperature, sound waves, fluid engineering, and pressure.
Many functional features may transfer short response times, low power consumption, dynamic spatial resolution, flexibility, and integration on various soft and hard surfaces.